摘要:
A modem communication system with receiving and transmission paths includes a direct equalizer system having an adaptive filter (1532) in the transmission path to compensate for frequency distortion of the communication channel. The transmitter filter coefficients are adapted by a filter coefficient calculator (1528), under control of a data detector (1526) which detects incoming data in the receiving path. A switch (1534) is controlled by status of a transmit output data buffer to multiplex either the training sequence or output data into the transmission path. When the buffer is idle, the training sequence generator (1540) is linked to a digital-to-analog (D/A) converter (1536) and line driver (1538). The receiving path includes an isolation switch (1520), a receiver amplifier (1522) and a slicer (1524). The receiver correlates the received training sequence with a known training sequence and updates the equalizer filter coefficients using an adaptation algorithm, such as a least mean squared algorithm. A first embodiment utilizes a high speed digital programmable filter (1532). Another embodiment utilizes a data buffer (1533) which is periodically filled with data filtered by a digital signal processor (DSP).
摘要:
A modem that operates selectively in the voice-band frequency band and at higher frequency bands is provided. This modem supports multiple line codes, like DMT and CAP. The modem uses a Digital Signal Processor (DSP), so that different existing ADSL line codes, such as Discrete MultiTone (DMT) and Carrierless AM/PM (CAP), can be implemented on the same hardware platform. The modem negotiates in real-time, for a desired line transmission rate to accommodate line condition and service-cost requirement. The line code and rate negotiation process may be implemented at the beginning of each communication session through the exchange of tones between the modems. A four-step MDSL modem initialization process is provided for line code and rate compatibility.
摘要:
An ultra low-power transmission system for use with a battery-operated device. The ultra-low power transmission system comprises an encoded transmitter and an addressable ultra -low power receiver. The ultra low-power receiver comprises an RF front-end block for receiving and demodulating an incoming RF signal. The RF front-end block includes an amplifier for amplifying the received RF signal and a frequency discriminator for demodulating the amplified RF signal to produce a baseband signal. The amplifier and the frequency discriminator are each comprised of enhancement mode, high-mobility electron transistors (E-HEMTs). The ultra low-power further receiver comprises a correlator for receiving the baseband signal from the frequency discriminator and detecting a codeword therein. The correlator comprises a plurality of switched capacitors for storing samples of the baseband signal. The correlator is operable to couple the plurality of switched capacitors in order to integrate the samples stored thereon.
摘要:
A method and protocol for dynamic downstream and upstream frequency assignment in a localized microwave distribution system. Downstream frequencies can be assigned via a base station periodic broadcast of a frequency assignment table for a home common control channel in each base station downstream frequency. Customer premise equipment monitors the home common control channel for a frequency assignment message, which preferably includes a table mapping each customer premise equipment, or that equipment for which there has been no recent upstream communication. Downstream frequencies may also be assigned by a customer premise equipment request to a base station sent over a common control channel associated with an upstream frequency associated with a downstream frequency identified during a scan of downstream frequencies. A modified aloha contention algorithm is used if multiple customer premise equipment requests conflict. Upstream frequency and time slot requests are done in similar fashion, with a customer premise equipment sending a request over either common control channel of a currently assigned upstream frequency or a common control channel associated with a downstream frequency with which the customer premise equipment is associated.
摘要:
A method and protocol for dynamic downstream and upstream frequency assignment in a localized microwave distribution system. Downstream frequencies can be assigned via a base station periodic broadcast of a frequency assignment table for a home common control channel in each base station downstream frequency. Customer premise equipment monitors the home common control channel for a frequency assignment message, which preferably includes a table mapping each customer premise equipment, or that equipment for which there has been no recent upstream communication. Downstream frequencies may also be assigned by a customer premise equipment request to a base station sent over a common control channel associated with an upstream frequency associated with a downstream frequency identified during a scan of downstream frequencies. A modified aloha contention algorithm is used if multiple customer premise equipment requests conflict. Upstream frequency and time slot requests are done in similar fashion, with a customer premise equipment sending a request over either common control channel of a currently assigned upstream frequency or a common control channel associated with a downstream frequency with which the customer premise equipment is associated.
摘要:
Multipoint Stations are controlled by one or more pilot tones broadcasted by a base station. The pilot tones are used to control the local oscillators of the remote stations both for receive and for transmit. The pilot tone is also used to control the input gain and the transmit gain of the remote station.
摘要:
A point-to-multipoint communication system wherein the base station broadcasts the same frequency band signals over multiple sectors of given node. The base station includes a plurality of channel receivers (ch. 1-ch. n) for each sector and a plurality of antennas 36a and 36b selectively coupled to said channel receivers. The subsector antennas have these radiation centers offset from each other to present different coverage over the node.
摘要:
A wireless communication system (100) is disclosed in which a central office (102) generates a signal. A first base station (104) receives the central office signal and transmits a first broadcast signal in a first frequency range in response to the central office signal. A second base station (124) receives the first broadcast signal and transmits a second broadcast signal in a second frequency range in response to the first broadcast signal. A third base station (134) receives the second broadcast signal and transmits a third broadcast signal in the first frequency range in response to the second broadcast signal. In accordance with the present invention, a plurality of base stations are each able to provide one-way or two-way communication to a plurality of customers (110, 130, 140), with only one base station (104) receiving signals directly from the central office (102).
摘要:
An antenna compensation system and method equalizes transmission link efficiency in sectors having unequal antenna or path gain while maintaining an equalized power spectral density. Areas of a sector having lower gains receive broadcasts with more robust coding to equalize their transmission link performance with areas of a sector having higher gains. The robustness of coding is controlled through setting of different forward error code rates, setting of different modulation types, or a combination of both. In analog systems it is controlled through variation of a signal-to-noise sensitive transmission parameter. Sectors may be divided azimuthally with areas at or near the boresight receiving less robust coding and areas nearer the sector edges receiving more robust coding. Similarly, sectors may be divided into radial areas with the more distant areas receiving more robust coding.